Using Sessions and HttpContext in ASP.NET 5 and MVC6

If you’ve started work on a new ASP.NET 5, MVC 6 application you may have noticed that Sessions don’t quite work the way they did before. Here’s how to get up and running the new way.

UPDATE: 2016-07-23 - ASP.NET Core 1.0
Sessions have changed again for ASP.NET Core 1.0 RTM. This post is still super useful for anyone migrating an old project, or still working on any of the betas or RC1, but for the latest you should go to my updated post: Using Sessions and HttpContext in ASP.NET Core and MVC Core.

UPDATE: 2015-11-05 - Beta8
I’ve updated this post to suit beta8. I keep these beta posts up to date, but if you find something that doesn’t work, be sure to use the links at the bottom for more information.

Remove DNX Core Reference

Many simple ASP.NET components aren’t supported by the DNX Core Runtime. These usually surface with weird build errors. It’s much easier to just remove it from your project.json file. If it’s already not there, beautiful you don’t need to do anything :)

"frameworks": {
    "dnx451": { },
    "dnxcore50": { } // <-- Remove this line
},

Add Session NuGet Package

Add the Microsoft.AspNet.Session NuGet package to your project.

VERSION WARNING: If you’re using ASP.NET 5 before RTM, make sure the beta version is the same across your whole project. Just look at your references and make sure they all end with beta8 (or whichever version you’re using).

Update startup.cs

Now that we have the Session nuget package installed, we can add sessions to the OWIN pipline.

Open up startup.cs and add the AddSession() and AddCaching() lines to the ConfigureServices(IServiceCollection services)

// Add MVC services to the services container.
services.AddMvc();
services.AddCaching(); // Adds a default in-memory implementation of IDistributedCache
services.AddSession();

Next, we’ll tell OWIN to use a Memory Cache to store the session data. Add the UseSession() call below.

// IMPORTANT: This session call MUST go before UseMvc()
app.UseSession();

// Add MVC to the request pipeline.
app.UseMvc(routes =>
{
    routes.MapRoute(
        name: "default",
        template: "{controller}/{action}/{id?}",
        defaults: new { controller = "Home", action = "Index" });

    // Uncomment the following line to add a route for porting Web API 2 controllers.
    // routes.MapWebApiRoute("DefaultApi", "api/{controller}/{id?}");
});

Where’s the Session variable gone?

Relax it’s still there, just not where you think it is. You can now find the session object by using HttpContext.Session. HttpContext is just the current HttpContext exposed to you by the Controller class.

If you’re not in a controller, you can still access the HttpContext by injecting IHttpContextAccessor.

Let’s go ahead and add sessions to our Home Controller:

public class HomeController : Controller
{
    public IActionResult Index()
    { 
        HttpContext.Session.SetString("Test", "Ben Rules!");
        return View();
    }

    public IActionResult About()
    {
        ViewBag.Message = HttpContext.Session.GetString("Test");

        return View();
    }
}

You’ll see the Index() and About() methods making use of the Session object. It’s pretty easy here, just use one of the Set() methods to store your data and one of the Get() methods to retrieve it.

Just for fun, let’s inject the context into a random class:

public class SomeOtherClass
{
    private readonly IHttpContextAccessor _httpContextAccessor;
    private ISession _session => _httpContextAccessor.HttpContext.Session;

    public SomeOtherClass(IHttpContextAccessor httpContextAccessor)
    {
        _httpContextAccessor = httpContextAccessor;
    }

    public void TestSet()
    {
        _session.SetString("Test", "Ben Rules!");
    }

    public void TestGet()
    {
        var message = _session.GetString("Test");
    }
}

Let’s break this down.

Firstly I’m setting up a private variable to hold the HttpContextAccessor. This is the way you get the HttpContext now.

Next I’m adding a convenience variable as a shortcut directly to the session. Notice the =>? That means we’re using an expression body, aka a shortcut to writing a one liner method that returns something.

Moving to the contructor you can see that I’m injecting the IHttpContextAccessor and assigning it to my private variable. If you’re not sure about this whole dependency injection thing, don’t worry, it’s not hard to get the hang of (especially constructor injection like I’m using here) and it will improve your code by forcing you to write it in a modular way.

But wait a minute, how do I store a complex object?

How do I store a complex object?

I’ve got you covered here too. Here’s a quick JSON storage extension to let you store complex objects nice and simple.

public static class SessionExtensions
{
    public static void SetObjectAsJson(this ISession session, string key, object value)
    {
        session.SetString(key, JsonConvert.SerializeObject(value));
    }

    public static T GetObjectFromJson<T>(this ISession session, string key)
    {
        var value = session.GetString(key);

        return value == null ? default(T) : JsonConvert.DeserializeObject<T>(value);
    }
}

Now you can store your complex objects like so:

var myComplexObject = new MyClass();
HttpContext.Session.SetObjectAsJson("Test", myComplexObject);

and retrieve them just as easily:

var myComplexObject = HttpContext.Session.GetObjectFromJson<MyClass>("Test");

Use a Redis or SQL Server Cache instead

Instead of using services.AddCaching() which implements the default in-memory cache, you can use either of the following.

Firstly, install either one of these nuget packages:

  • Microsoft.Framework.Caching.SqlServer
  • Microsoft.Framework.Caching.Redis

Secondly, add the appropriate code snippet below:

// Microsoft SQL Server implementation of IDistributedCache.
// Note that this would require setting up the session state database.
services.AddSqlServerCache(o =>
{
	o.ConnectionString = "Server=.;Database=ASPNET5SessionState;Trusted_Connection=True;";
	o.SchemaName = "dbo";
	o.TableName = "Sessions";
});

 

// Redis implementation of IDistributedCache.
// This will override any previously registered IDistributedCache service.
services.AddSingleton<IDistributedCache, RedisCache>();

Stay up to date

Since the API’s are still in beta at the time of writing, you should keep an eye on the ASP.NET Session Repository for any changes. Here’s a direct link to the Sample code.